Model-free methods of linkage analysis do not rely on a priori knowledge of the mode of inheritance of a disease and are thus ideal for mapping susceptibility loci for complex diseases. A reparameterization of the affected-sib-pair likelihoods of Risch has been proposed. The new parameterization is in terms of variance components and is easily extended to the study of multiple disease loci and their interactions. We are currently investigating a general framework that allows multilocus modeling of sib pair data obtained under a wide variety of sampling strategies. The models are suitable for both affected sib pairs and for quantitative traits.